Comments

at the moment R. oportense is the best name for it; By the reasons you mentioned and also by exclusion of the other parts in the yellow Rizocarpon spp..
Thanks for uploading the new observations:
1) The K reaction of R. eupetraeum is clear enough;
2) The non K reaction of R. obscuratum is also very clear, no shade of red!
This one is also interesting because at the first sight this could be taken by a Lecidea and secondly because, if you remember, it is the only non yellow Rizocarpon sp. appearing in the “checklist” for this place (so, now I know what to look for!).
Thanks, Jason, for the comments.

Personally, I prefer not to rule out a name based only on a difference in one minor character

If MO accepted the “cf.” notation, then it might be best to call this “Rhizocarpon cf. oportense”. Becuase it almost matches that species, it’s just this pesky K+y epihymenium reaction fouling things up.

Once you see the real thing — preferably the type specimen itself! — then you can better decide if there are additional characters which also differ in some way. “Correlated differences” is one of the standard “rules of thumb” for deciding if a subpopulation represents a new (undescribed) species. But at the moment, this K+y epihymenium is the only thing we have to go on. That just doesn’t feel like enough to me. It may be that this character was misreported in Runemark 1956, or that there is variation Runemark didn’t see. Who knows?

Therefore, and given MO’s constraints, I think R. oportense is the best name to apply to this observation. But I would certainly understand being conservative and leaving it at R. viridiatrum group instead. Your call!

(I just uploaded an old observation of R. eupetraeum showing the K+r reaction you’re looking for. See observation 201886. This is a particularly strong one.)

I upload two new photos, one with spores where the internal septation is better visible than before and the other on the account of two other issues:
1) I repeated the K reaction on a section with the same result. The photo attached was taken while the K reaction was developing; One can see there some yellow stain at the top; On the other hand, one can also see that redish tones exist everywhere on the hymenium, but this is the natural coloration of it and I didn’t saw any reinforcement caused by the addition of K; Moreover, particularly on the epihymenium no redish tone was accentuated.
In the old paper by H. Runemark, that Jason was kind enough to send me, I saw that in the “Viridiatrum group” there are two species that have stictic acid: R. oportense and R. tetrasporum; Regarding Lichen subtances, for the former it is written “Rhizocarpic acid, sometimes stictic acid” and for the latter “Rhizocarpic acid, stictic acid”. If my comment below is valid, then one can rule out R. tetrasporum. Is it possible that a low concentration of Rhizocarpic acid together with the presence of stictic acid prevents the development of the red reaction?
2) The photo also shows some spores still inside the asci; It is not possible to say how many they are, but certainly more than four; From the all observation I suspect that most probably these are (6-)8-spored, due to the accumulation of spores at certain places.

I performed the K reaction on a section and it was K+ YELLOW. The outermost part of the epihymenium reacted K+ yellow (clearly); The hymenium didn’t react; the hypohymenium also reacted K+ yellow, though not so strong as in the epihymenium
I never heard or saw such reaction. What is its meaning?

Ah, but that’s just because you have such a good eye for interesting and beautiful lichens!

But as you can see from my observations from this locations that there are many more species there that do not appear in this small list; this is my conviction.
My deep acknowledgement for you help, Jason.

R. obscuratum is a small, purplish-gray species with I+v medulla, K+r epihymenium, 8 spores per ascus, spores 3-septate to barely muriform hyaline to finally gray or brown only when dead or overmature. It’s often tiny and mixed with other species. I’ve seen it a hundred times in eastern Washington, but I’m still searching hopefully for a photogenic specimen!

As you know we don’t a proper ckecklist, but there are places that where investigated by lichenologists. This location is one of them and the paper given below serves as a checklist for it, though it was publish at the end of the last century. Here are the species of Rhizocarpon mentioned there:R. geographicum (L.) D CR. lecanorinumANDERSR. macrosporum RÄSÄNENR. obscuratum (ACH.) MASSAL.R. oportense (VAINIO) RÄSÄNEN
So, the proposal of R. oportense seems plausible. Of course, I have to check the K-reaction on epihymenium, that I’ll do as soon as possible.

If the epihymenium turns reddish (maybe with a violet/purple tinge) in K, then I think you’ve got a positive id.

For what it’s worth, this does in fact look a lot like R. cookeanum, which so far as I can tell is the North American version of R. oportense. (Ours has 2 spores per ascus, but otherwise macroscopically and microscopically looks identical.)

I personally cut a thick vertical section from an areole including at least some white/yellow medulla below the algal layer. Place this on a slide next to a drop of Lugol’s solution, then apply the Lugols with a needle while watching through a dissecting scope. An amyloid reaction is very distinct, causing the medulla to turn dark violet-black immediately. Negative is anything from reddish to yellowish to brownish or unchanged.

Of course, there are a dozen different ways of performing the test, but I think it’s good – whatever you choose – to keep it as consistent as possible. This method has worked very well for me… and better than some other methods I’ve tried.

I never found or knew about Tephromela armeniaca, but this one is certainly a Rhizocarpon with muriform spores (I just looked at them under the microscope). So, according you proposal, this must belong to R. viridiatrum group. Let’s wait and see.
Thanks, Jason, once again for the hints.